Screw rotor machine for compressible media

ABSTRACT

A screw rotor machine for compressible media comprising a driving and at least one driven rotors with conjugated profiles of the addendum of the tooth of the driven rotor and the dedendum of the tooth of the driving rotor. The profile of the flank face of the addendum is a section of an epicycloid butted to a section of an elongated hypocycloid.

United States Patent Amosov et al.

[54] SCREW ROTOR MACHINE FOR COMPRESSIBLE MEDIA [72] Inventors: Pavel Evgenievich Amosov, ulitsa Kronverxkaya, 29/37, kv. 87; Vitaly Konstantinovich Smekhov, ulitsa Kolomenskaya, 33/40, kv. 25; Valery Leonidovich Troflmov, ulitsa Matrosova, l2, kv. 8, all of Leningrad; Avely Isaich Shvarts, ulitsa Kosmonavtov, 3, kv. 45; Vladimir Borlsovieh Shnepp, ulitsa Zarya, 4, kv. 5, both of Kazan; Alexandr Petrovich Razumovsky, Drovyanoi pereulok, 3, kv. 3, Leningrad, all of U.S.S.R.

[22] Filed: May 20,1971

[21] Appl.No.: 145,179

[52] US. Cl ..418/191, 418/201 [51] Int. Cl ..F0lc 1/16, F010 1/08, F010 17/12 [58] Field ofSearch ..418/l9l,20l

us] 3,692,441 51 Sept. 19, 1972 [56] References Cited UNITED STATES PATENTS 2,462,924 3/ 1949 Ungar ..418/201 3,170,566 2/1965 Zimmermann ............418/201 3,283,996 11/ 1966 Schibbye ..418/201 3,305,167 2/1967 Nagata ..418/191 Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney-Waters, Roditi, Schwartz & Nissen 5 7] ABSTRACT A screw rotor machine for compressible media comprising a driving and at least one driven rotors with conjugated profiles of the addendum of the tooth of the driven rotor and the dedendum of the tooth of the driving rotor. The profile of the flank face of the addendum is a section of an epicycloid butted to a section of an elongated hypocycloid.

1 Claim, 3 Drawing Figures SCREW ROTOR MACHINE FOR COMPRESSIBLE MEDIA The present invention relates to devices for compression of compressible media as well as for converting the energy of a compressed medium into mechanical energy. More particularly, the invention relates to screw rotor machines for compressible media.

Known in the art is a screw rotor machine consisting of a housing accommodating driving and driven rotors interacting with each other and with the housing. The profile of the addendum flank face of the driven rotor in transverse section is formed by an arc of a circle lying on the pitch circle of the driven rotor. The dedendum profile of the driving rotor is conjugate to the addendum profile of the driven rotor.

The compression of the medium in the machine is effected by reducing the volume of spaces separated from the inlet branch pipe. These spaces are formed by the faces of the driving and driven rotors and the surface of the housing which represents a surface of two intersecting right cylinders having parallel axes. To provide for tightness of these spaces during the compression of the medium, it is necessary to provide for a contact of a rotors faces both between each other and with the surface of the housing. In this case the common line of contact of the faces of the rotors and of the housing surface is needed to be continuous.

The known rotor machine is disadvantage in that it has an interrupted common line of contact due to fact that the engagement of the teeth of the rotors is not exactly a point epicycloidal engagement and also in the presence of the addendum portions on the teeth of the driven rotors causing the formation of a spatial channel or, so called, triangular slot, which in the process of compression of the medium communication the rotors spaces with each ocher and with the outlet branch pipe of the machine. The presence of the triangular slot" disturbs the axial tightness of the screw rotor machine which is much higher than in a hypothetical case, when the addendum flank face of the driven rotor is formed by a section of a radial curve.

Another disadvantage of the known screw rotor machine consists in a variable gear ratio which results in higher gaps between the real profiles of the teeth.

Furthermore, the known screw rotor machine is charatcterized by a broken profile of the tooth of the driving rotor on the initial circle thereof, and this is associated with difficulties in manufacture of the screw portion of the rotor, particularly at large helix angles.

The above disadvantages adversely affect the efficiency and reliability of the machine.

An object of the present invention is to provide a screw rotor machine, in which the profile of the flank face of the addendum of the driven rotor would allow the triangular slot" to be reduced and also would provide for a constant gear ratio and a high efficiency of the process of manufacture of the screw portion of the driving rotor.

This object is attained due to the fact that in the screw rotor machine for compressible media, accord ing to the invention, the profile of the flank face of the addendum of the tooth of the driven rotor is a section of an epicycloid butted with a section of an elongated hypocycloid which is formed by rolling a generating circle, the radius of which exceeds a half of the addendum of the driven rotor but is less than a half of the radius of the pitch circle of the driving rotor, along the pitch circle of the driven rotor, while the elongated hydrocycloid is formed by rolling the generating circle along the inner side of the pitch circle of the driven rotor with a point located not on the periphery of the generating circle whose radius exceeds zero but is less than the radius of the pitch circle of the driven rotor.

The present invention will be apparent from the following description of one particular embodiment of the invention, reference being made to the accompanying drawings, in which:

FIG. 1 is a transverse section of the screw rotor machine according to the invention;

FIG. 2 is a flank face of the addendum of the tooth of the driven rotor according to the invention;

FIG. 3 is a sectional view taken along the line Ill-Ill IN FIG. 1.

The screw rotor machine for compressible media has a housing 1 (FIG. 1) incorporating a driving rotor 2 and a driven rotor 3. The teeth of the driven rotor 3 have a dedenum of at least of the tooth height and an addendum 4, while the teeth of the driving rotor 2 have addendums 5 and dedendums. The driven rotor 3 must be equipped with at least three teeth.

The dotted line illustrates a line 6 of action of the rotors 2 and 3 engaging each other. Lines 7 and 8 are lines of action of the rotors 2 and 3 with the housing 1. The lines of action consist of projections of the spatial lines of contact of the rotors and the housing onto an end plane.

In the known screw rotor machines the lines 6, 7, and 8, if taken separately, are continuous. However, as it is seen from their mutual location, when butting these lines, the common line of contact is interrupted.

One of the reasons responsible for the interruption of the common line of contact is the presence of the addendums 4 of the teeth of the driven rotor 3. The minimum distance between the lines 6, 7, and 8 of action, hence between the lines of contact, occurs between the branch points 0 and M, the incoincidence of which is caused by the presence of a spatial channel between the faces of the rotors 2 and 3 and the surface of the housing 1. The minimum secton of the channel, i.e. triangular slot" is in the secant plane YOZ passing through the branch points 0 and M of the action lines 6,7, and 8 parallel to the axis of rotation of the rotors 2 and 3.

FIG. 2 is a transverse section of the flank face of the addendum 4 of the tooth of the driven rotor 3 which is a section of an epicycloid A C, smoothly butted with a section of an elongated hypocycloid C,B,. The section of the epicycloid A,C, is formed by rolling the generating circle 9 along the periphery of the pitch circle 10 of the driven rotor 3 (FIG. I) with a drawing point 8' (FIG. 2) lying on the circle 9.

The radius of the generating circle 9 must be in excess of a half of the addendum 4 but less than a half of the radius of the pitch circle II (FIG. 1) of the driving rotor 2. The section of the elongated hypocycloid C 8, (FIG. 2) is formed during the rolling of the generating circle 12 along the inner side of the pitch circle 10 of the driven rotor 3 (FIG. I) by a drawing point S" (FIG. 2) spaced from the center of the circle 12 for a distance equal to the sum of the addendum 4 of the tooth and the radius of the generating circle 12. The radius of the generating circle 12 must be in excess of zero but less than the radius of the pitch circle of the driven rotor 3 (FIG. 1).

the triangular slot" of the screw rotor machine whose teeth have the above-described shape is formed by the lines l3, l4 and (FIG. 3).

The line 13 is a section of the face of the tooth of the driving rotor 2 (FIG. 1) by the secant plane YOZ. The line 14 (FIG. 3) is a section of the surface of the housing (FIG. 1) by the secant plane YOZ. The line 15 (FIG. 3) is a section of the face of the tooth of the driven rotor 3 (FIG. 1) by the secant plane YOZ.

In the known screw rotor machine the triangular slot" is formed by the lines 13,14,16, where the line 16 is a section of the face of the tooth of the driven rotor by the secant plane YOZ (FIG. 1). FIG. 3 shows that the triangular slot has a considerable size.

In order to reduce the gap between the screw portion of the driven rotor 3 and the housing 1, the tops of the addendums 4 of the teeth of the rotor can be provided with sealing crests (not shown) which provide for a reliable operation of the machine with an increased angular slot". In this case the sealing grooves are made in the tooth spaces of the driving rotor. The profiles of the sealing crests and grooves are conjugated and this provides for a continuity of the line of contact of the screw portions of the driving rotor 2 and the driven rotor 3.

The profile of the flank face of the sealing crest in transverse section may consist of a section of a shortened epicycloid which is formed by rolling the generating circle along the pitch circle 10 of the driven rotor 3. The radius of the generating circle is equal to the radius of the pitch circle I] of the driving rotor 2.

In the process of operation of the screw rotor machine the medium filling the spaces formed by the faces of the driving and driven rotors 2 and 3 as well as by the surface of the housing 1, changes its volume during the rotation of the rotors 2 and 3 and moves from the inlet branch pipe of the machine to the outlet branch pipe of the same (the branch pipes are not shown).

In this case, due to the fact that the profile of the flank face of the addendum 4 of the tooth of the driven rotor 3 is formed by the section of an epicycloid smoothly butted with the section of an elongated hypocycloid, the area of the triangular slot" is reduced as compared with the known machine, the length of the line of contact of both practically the same. The decrease in the area of the "triangular slot" reduces the leakage of the medium between the spaces of the rotors 2 and 3 in the process of compression and improves the efficiency of the compression (expansion).

In addition, the proposed screw rotor machine is featured by a constant gear ratio which improves the efficiency of the process of compression (expansion) and increases the amount of working medium passing through the inlet branch pipe of the machine per revolution of driving rotor wheel. In the proposed machine the profile of the driving rotor is not interrupted and this considerably increases the wear resistance of the cutting tool used for making rotor, thus reducing the cost of manufacture of the proposed screw rotor machine and increasing its reliability in operation.

We claim: l. A screw rotor machine for compressible media comprising in combination: a housing, a driving rotor mounted within said housing; a driven rotor mounted within said housing and interacting with said driving rotor: teeth of said driving rotor; dedendums of said teeth of the driving rotor; teeth of said driven rotor; addendums of said teeth of the driven rotor having a profile conjugate to the profile of said dedendums of the teeth of the driving rotor, in which case the profile of the flank face of said addendums of the tooth is a section of an epicycloid butted to a section of an elongated hypocycloid, said epicycloid is formed by rolling a generating circle, the radius of which exceeds a half of the addendum of the driven rotor but is less than a half of the radius of the pitch circle of said driving rotor, along the pitch circle of said driven rotor, while said elongated hypocycloid is formed by rolling a generating circle along the inner side of the pitch circle of said driven rotor with a point located not on the periphery of said generating circle, the radius of which exceeds zero but is less than the radius of said pitch circle of the driven rotor. 

1. A screw rotor machine for compressible media comprising in combination: a housing, a driving rotor mounted within said housing; a driven rotor mounted within said housing and interacting with said driving rotor: teeth of said driving rotor; dedendums of said teeth of the driving rotor; teeth of said driven rotor; addendums of said teeth of the driven rotor having a profile conjugate to the profile of said dedendums of the teeth of the driving rotor, in which case the profile Of the flank face of said addendums of the tooth is a section of an epicycloid butted to a section of an elongated hypocycloid, said epicycloid is formed by rolling a generating circle, the radius of which exceeds a half of the addendum of the driven rotor but is less than a half of the radius of the pitch circle of said driving rotor, along the pitch circle of said driven rotor, while said elongated hypocycloid is formed by rolling a generating circle along the inner side of the pitch circle of said driven rotor with a point located not on the periphery of said generating circle, the radius of which exceeds zero but is less than the radius of said pitch circle of the driven rotor. 